The present invention relates to a photosensitive resin composition for use as a material for printed wiring boards and a photosensitive resin as a component of the above photosensitive resin composition. The photosensitive resin composition of the present invention is suitable for use as a material which has excellent resolving performances and high heat durability and which shows excellent heat durability and electric insulation in a humidified state.
In recent years, it is desired to downsize and compact electronic machines and equipment, and it is therefore as well essential to comply with downsizing, a higher fineness and a decrease in weight and thickness with regard to printed wiring boards. A solder resist material to be applied onto a substrate has been generally selected from those materials which are ultraviolet-curable and developable with a diluted alkali and which is excellent in durability against soldering and solvents. However, xe2x80x9cbuild-upxe2x80x9d substrates having fine wirings inside recently come to encounter problems in the heat-resistance of a solder resist, such as a popcorn phenomenon which is caused between a solder resist/sealing resin interface. Further, it is also demanded to increase insulation reliability between lines of a closely packed wiring.
For improving electric insulation and heat resistance, there has been developed a resist containing a cyanate ester compound such as a bismaleimide-triazine resin (BT resin) (Japanese Patent Application No. 08-298641).
A cyanate ester compound is caused to remain during alkali development, and the steps of electroless nickel plating and electroless gold plating after the resist is applied is caused to have a problem.
It is an object of the present invention to provide a photosensitive resin which can give a photosensitive resin composition having high heat durability and excellent heat durability and electric insulation in a humidified state and having alkali-developability and developability free of problems caused during electroless plating, and a photosensitive resin composition containing the above photosensitive resin.
According to the present invention, there is provided a photosensitive resin (B) which is a reaction product produced by reacting an epoxy acrylate (a) with a cyanate ester compound (b) to obtain a reaction product (A) and reacting the reaction product (A) with a polybasic acid anhydride (c).
According to the present invention, further, there is provided a photosensitive resin composition comprising the above photosensitive resin (B) and an epoxy resin (d).